Re: [PATCH 2/2] mmc: sdhci-of-dwcmshc: reduce CIT for better performance

[Adrian Hunter <adrian.hunter@intel.com>]

On 12/11/2025 14:03, Ulf Hansson wrote:
> + cqhci maintainers (Adrian, Asutosh, Ritesh)
> 
> On Wed, 12 Nov 2025 at 08:44, Shawn Lin <shawn.lin@rock-chips.com> wrote:
>>
>> CQHCI_SSC1.CIT indicates to the CQE the polling period to use for
>> periodic SEND_QUEUE_STATUS (CMD13) polling. Some eMMCs have only one
>> hardware queue, and CMD13 can only query one slot at a time for data
>> transmission, which cannot be processed in parallel. Modifying the
>> CMD13 query interval can increase the query frequency and improve
>> random write performance.
>>
>> Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
> 
> No strong opinion on this, but I looped in the cqhci maintainers to
> allow them to chime in.

cqhci-core leaves CQHCI_SSC1 configuration to the default values
or for drivers to set for themselves.  When it comes to timing
values, eMMC has not really been one-size-fits-all, so that seems
appropriate.

So for both patches:

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

> 
> Kind regards
> Uffe
> 
>> ---
>>
>>  drivers/mmc/host/cqhci.h            | 1 +
>>  drivers/mmc/host/sdhci-of-dwcmshc.c | 5 +++++
>>  2 files changed, 6 insertions(+)
>>
>> diff --git a/drivers/mmc/host/cqhci.h b/drivers/mmc/host/cqhci.h
>> index ce189a1..3668856 100644
>> --- a/drivers/mmc/host/cqhci.h
>> +++ b/drivers/mmc/host/cqhci.h
>> @@ -93,6 +93,7 @@
>>  /* send status config 1 */
>>  #define CQHCI_SSC1                     0x40
>>  #define CQHCI_SSC1_CBC_MASK            GENMASK(19, 16)
>> +#define CQHCI_SSC1_CIT_MASK            GENMASK(15, 0)
>>
>>  /* send status config 2 */
>>  #define CQHCI_SSC2                     0x44
>> diff --git a/drivers/mmc/host/sdhci-of-dwcmshc.c b/drivers/mmc/host/sdhci-of-dwcmshc.c
>> index e276a4e..cad5165 100644
>> --- a/drivers/mmc/host/sdhci-of-dwcmshc.c
>> +++ b/drivers/mmc/host/sdhci-of-dwcmshc.c
>> @@ -631,6 +631,11 @@ static void rk35xx_sdhci_cqe_pre_enable(struct mmc_host *mmc)
>>         struct dwcmshc_priv *dwc_priv = sdhci_pltfm_priv(pltfm_host);
>>         u32 reg;
>>
>> +       /* Set Send Status Command Idle Timer to 10.66us (256 * 1 / 24) */
>> +       reg = sdhci_readl(host, dwc_priv->vendor_specific_area2 + CQHCI_SSC1);
>> +       reg = (reg & ~CQHCI_SSC1_CIT_MASK) | 0x0100;
>> +       sdhci_writel(host, reg, dwc_priv->vendor_specific_area2 + CQHCI_SSC1);
>> +
>>         reg = sdhci_readl(host, dwc_priv->vendor_specific_area2 + CQHCI_CFG);
>>         reg |= CQHCI_ENABLE;
>>         sdhci_writel(host, reg, dwc_priv->vendor_specific_area2 + CQHCI_CFG);
>> --
>> 2.7.4
>>